We propose to elucidate the bearing the natural immune system, the maturational state of the sperm surface andovarian hormonal control of capacitation have on regulation of sperm function and so fertilization in the female. Since pilot studies implicate the complement system in some aspects of sperm distribution in the normal female rabbit, we will examine the levels of complement components in the rabbit oviduct and uterus, and, by decomplementation, then the degree to which this mediates the pattern of sperm transport, their selection and their clearance from the tract. A further aspect will probe the effect of complement depletion on the leucocyte mobilization response to spermatozoa, the basis of the normal absence of this response to spermatozoa in the oviduct, and whether white cells affect oocytes when mobilized there. Our finding that decomplementation allows significantly greater numbers of spermatozoa to reach the site of fertilization will be exploited to verify ultrastructurally whether the acrosome reaction is essential for early sperm passage through intact cumulus oophorus. Whether decomplementation will negate the inhibition of fertilization that occurs in females immunized against homologous spermatozoa and, conversely, the possibility that insemination of complement-depleted females will evoke an active immunization response to spermatozoa, will also be explored. How the maturational state of the sperm surface relates to sperm function will examined with special reference to leucocyte mobilization and selective disposal of spermatozoa in the female, and by use of hetero-antibody to sperm coating epididymal glycoprotein so as to analyze its possible relationship to capacitation and sperm/egg interaction. It remains uncertain is sperm capacitation in the Fallopian tube can be controlled endocrinologically since results in an induced ovulator, the rabbit - the major model in this respect - have been negative. Following equivocal results in a cyclic rodent, we will establish whether the capacitation potential of the oviduct can be suppressed completely in a cyclic primate, the squirrel monkey, as a step to ultimate analysis of the factors that capacitate spermatozoa. This research will foster a more rational approach to control of sperm function in the female tract for alleviation of infertility and particularly for contraception.